Nineteen people have died in an outbreak of more than 500 cases of hepatitis A in San Diego, according to public health officials.
It is the second largest outbreak in the United States since a vaccine was approved in the 1990s, and it has spurred California to declare a state of emergency.
The outbreak, which began unfolding in November, is hitting the homeless population and those with limited access to sanitation particularly hard, according to the Associated Press.
Hepatitis A is a liver infection caused by a highly contagious virus. The most common outbreaks come from food contamination, but according to the AP, the surge currently being experienced in California is caused by a strain rare in the United States that is spread by contact with fecal matter. San Diego County has installed hand-washing stations and portable toilets around the areas where homeless people gather, and crews are cleaning the streets.
California Gov. Jerry Brown declared a state of emergency Friday in order to allow the state to buy vaccines from distributors rather than rely on federally funded supplies, which he said are insufficient. The county has vaccinated thousands of people who are homeless or who frequently use drugs.
The vast majority of the cases are in San Diego, but dozens of other cases have been found in Santa Cruz County and some have been found in Los Angeles. Officials say the outbreak could continue for a year or more.